This invention relates to a new, stabilized, storable, fluid lawn fertilizer which provides for the slow, efficient, release of nitrogen so that large amounts of fertilizer may be applied directly without burning injury or wasteful loss of nutrients. More particularly, it relates to the composition of a storable suspension of high urea formaldehyde polymers stabilized for storage by its composition, and by alcohol and sugar additives.
Liquid mixed fertilizers are normally solutions of chemicals which are soluble in water and supply the primary plant nutrients; namely, nitrogen, phosphorous, and potassium. The present invention is directed primarily to suspensions containing all three primary nutrients and necessary secondary and micronutrients. Unlike normal liquid mixed fertilizers, most of the nitrogen content in the present invention is water insoluble while most of the phosphorous, and potassium is soluble.
Problems in growing grasses, as well as crops, have long been associated with the lack of a fertilizer which would allow direct application of the economically required amount of plant foods without plasmolysis, or damage to the plants. The damage to the plant is usually caused by contact with the foliage, or excess root uptake of the soluble nitrogen. The damage to the grasses usually takes the form of foliage burn, where the grass turns yellow, or if the burn is severe, the grass is killed.
The art of applying complete fertilizers containing nitrogen to grasses was advanced by the development of solid urea formaldehyde polymer based fertilizers which had reduced burning tendencies when evenly applied to grasses. One of the early developments in this area was U.S. Pat. No. 2,827,368, Everett N. Mortenson et al, entitled, "Non-Burning Plant Fertilizer". There are now several slow-release urea formaldehyde based solid fertilizers produced and marketed commercially in the United States. Although these products do provide delayed release of much of the nitrogen, the nitrogen content is not efficiently used because of inherent problems in obtaining even distribution of solids, and in obtaining even release of nitrogen from the wide range of urea-formaldehyde polymer molecular weights contained in the solids.
Many workers have reported efforts to apply the efficient liquid techniques in this field. U.S. Pat. No. 3,119,683 by Joseph P. Kealy reported that urea-formaldehyde solutions, containing 1/1 to 2.75/1 urea to formaldehyde mol ratio with 25% or less water, and pH 6.8-7.3 at 30.degree.-250.degree. C. were stable for 24 hours or less. This product was water soluble and would quickly release its nitrogen and burn turf if it were applied in significant amounts. In subsequent U.S. Pat. No. 3,235,370 Kealy provided a product which was storable for about 30 days by adding strong base. This product was an improved ingredient for producing solid urea-formaldehyde fertilizers but was not suitable for direct application. Hewson in U.S. Pat. No 3,183,200 advanced the art of urea-formaldehyde fertilizers further by providing a practical process for storable urea-formaldehyde water soluble concentrates.
Charles E. Waters in U.S. Pat. No. 3,096,168 advanced the fertilizer art by preparing suspensions of urea-formaldehyde in liquid mixed fertilizer containing appreciable amounts of water insoluble nitrogen. These suspensions of urea-formaldehyde in water were prepared by reacting 1 to 2.5 mols of urea per mol of formaldehyde under acid conditions along with other water soluble fertilizer ingredients. Typically, a practical product from U.S. Pat. No. 3,096,168 contained only 1.8% water-insoluble nitrogen. Although the water insoluble nitrogen content of U.S. Pat. No. 3,096,168 was appreciable, in several cases almost 5% N, the still higher water soluble nitrogen content made the product likely to burn grasses when applied directly at commercially desirable rates.
The art of producing fluid fertilizers containing water-insoluble nitrogen was further advanced by U.S. Pat. No. 3,677,736 by Richard E. Formaini which provided preparation methods by which liquid fertilizer suspensions containing urea formaldehyde polymers having high activity indices can be prepared. It does not allow conversion of substantially all of the nitrogen in the fluid fertilizer to water-insoluble form.
Neither of the fluid products from U.S. Pat. Nos. 3,096,168 or 3,677,736 may be stored for commercially required periods of time, and both products contain large portions of water soluble nitrogen which would cause hazard of foliage burn if applied directly to grasses particularly in hot, dry weather.
The use of fluid delayed release nitrogen fertilizers on grasses and lawn foliage is most desirable from the standpoints of economics, efficacy, and ease of application. There has been to date little commercial use of this type of product.
Problems with existing art which prevent commercialization are:
(1) When the urea-formaldehyde polymerization is not carried far enough to convert most of the nitrogen to water-insoluble form, direct application, especially on grass foliage, causes burning by the water nitrogen.
(2) When urea-formaldehyde polymerization is carried far enough to convert most of the nitrogen to the water-insoluble form to prevent burning, the release of the water-insoluble nitrogen is delayed for such an extended period that it is either physically or chemically lost from the crop site before it is used.
(3) Urea-formaldehyde water-insoluble polymer suspensions produced to date have not been stable enough for even limited storage periods. The polymers continue to grow in molecular weight and within several days, the fluid fertilizer turns into a semi-solid which cannot be handled in pipes, pumps, nozzles, and tanks. The use of highly diluted products to prevent gelling and solids formation, results in the urea-formaldehyde polymers settling out rapidly to the bottom of the storage of distribution tanks.
In view of the foregoing, it is an object of this invention to provide an improved, storable, liquid, urea-formaldehyde-based lawn fertilizer composition which is safe for direct application to grass turfs.
It is another object of this invention to provide a liquid urea-formaldehyde-based fertilizer which releases polymerized nitrogen to grasses, and other plants, in an efficient and timely manner.
It is another object of this invention to provide an improved fluid urea-formaldehyde-based fertilizer which does not settle or separate and may be stored, handled, diluted, and applied effectively to lawns and to crops in practical and commercially available liquid fertilizer equipment.
Other objects and advantages of the present invention will be evident from the following description of the invention.